could sustain
Verbo regular: sustain - sustained- sustained

Afirmación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could sustain
you could sustain
she could sustain
we could sustain
you could sustain
they could sustain 	I could be sustaining
you could be sustaining
she could be sustaining
we could be sustaining
you could be sustaining
they could be sustaining	I could have sustained
you could have sustained
she could have sustained
we could have sustained
you could have sustained
they could have sustained	I could have been sustaining
you could have been sustaining
she could have been sustaining
we could have been sustaining
you could have been sustaining
they could have been sustaining	

Negación 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
I could not sustain
you could not sustain
she could not sustain
we could not sustain
you could not sustain
they could not sustain 	I could not be sustaining
you could not be sustaining
she could not be sustaining
we could not be sustaining
you could not be sustaining
they could not be sustaining	I could not have sustained
you could not have sustained
she could not have sustained
we could not have sustained
you could not have sustained
they could not have sustained	I could not have been sustaining
you could not have been sustaining
she could not have been sustaining
we could not have been sustaining
you could not have been sustaining
they could not have been sustaining	

Forma interrogativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I sustain?
could you sustain?
could she sustain?
could we sustain?
could you sustain?
could they sustain? 	could I be sustaining?
could you be sustaining?
could she be sustaining?
could we be sustaining?
could you be sustaining?
could they be sustaining? 	could I have sustained?
could you have sustained?
could she have sustained?
could we have sustained?
could you have sustained?
could they have sustained? 	could I have been sustaining?
could you have been sustaining?
could she have been sustaining?
could we have been sustaining?
could you have been sustaining?
could they have been sustaining? 	

Forma interro-negativa 	
Forma simple 	Forma con V-ing 	Perfecto 	Perfecto con V-ing 	
could I not sustain?
could you not sustain?
could she not sustain?
could we not sustain?
could you not sustain?
could they not sustain? 	could I not be sustaining?
could you not be sustaining?
could she not be sustaining?
could we not be sustaining?
could you not be sustaining?
could they not be sustaining? 	could I not have sustained?
could you not have sustained?
could she not have sustained?
could we not have sustained?
could you not have sustained?
could they not have sustained? 	could I not have been sustaining?
could you not have been sustaining?
could she not have been sustaining?
could we not have been sustaining?
could you not have been sustaining?
could they not have been sustaining?